Effect of two dosages of d-cloprostenol on intrauterine pressure and uterine motility during dioestrus in experimental cows

Prostaglandins are commonly used in herd management for their luteolytic pr operties; however, prostaglandins also have a direct contractile effect on the myometrium. We hypothesized that different dosages (0.15 and 0.3 mg) of d-cloprostenol, a synthetical prostaglandin F-2 alpha preparation, would d iffer as to their contractile effects on the uterus. Intrauterine pressure was recorded during dioestrus of lactating dairy cows, using a transcervica lly placed intraluminal pressure microtransducer. After recording of physio logical uterine motility for 30 min, a placebo or d-cloprostenol at one of the two different dosages was administered intramuscularly, followed by a 2 -h recording period. Significant differences were found for the area under the curve (P less than or equal to 0.05) and mean amplitude (P less than or equal to 0.05), whereas the number of spikes per 15 min and the baseline p ressure during the last 3 min of every 15-min period did not differ signifi cantly among treatments. Teak values for area under the curve and mean ampl itude were found between 15 and 30 min after administration of the lower do sage of d-cloprostenol, and between 75 and 90 min after administration of t he higher dosage. Using the higher dosage of d-cloprostenol, a steady plate au from 15 to 30 min after administration until the end of the recording se ssion was obtained. Thus, double the luteolytic dose of the d-cloprostenol preparation gives a significantly better reaction in terms of uterine contr actility than the single dose.